Modulation system



May 24, 1938- J. D. DURKEE Erm. 2,118,040

MODULATION SYSTEM Filed July 24, 1935 ATTORNEY Patented May 24, 1938MODULATION SYSTEM James D. Durkee, Bartlesville, Okla., and Edward H.Yonkers, Chicago, Ill., assignors to Phillips Petroleum Company,Bartlesville, Okla., a corporation of Delaware Application July 24,1935, Serial No. 32,951

Our invention relates broadly to carrier modulating systems and moreparticularly to a system employing a mechanical oscillator forgenerating the carrier.

One of the objects of our invention is to provide means for generating ahigh frequency alternating voltage at intensities proportional at anyinstant to the amount of flux in a eld of varying intensity.

Another object of our invention is to provide means for generating ahigh frequency carrier modulated in accordance with signal energy.

Still another object of our invention is to provide means for modulatingthe magnetic field of an induction generator without distortion, wherebya modulated high frequency voltage is produced in the inductiongenerator.

A further object of our invention is to provide an arrangement of eldstructure in an induction generator, which produces a magnetic field ofvarying intensity unaffected by the flux valving means of the inductiongenerator, whereby an undistorted modulated wave is generated.

A still further object of our invention is to provide an arrangement ofcore structure in an induction generator employed in a modulatingsystem, which involves only shifting of the ux in position in a magneticcircuit of constant reluctance thereby preventing distortion of themodulated output of the system.

Still another object of our invention is to provide means for generatinga modulated carrier voltage by modulating the magnetic eld of a highfrequency mechanical oscillator.

Other and further objects of our invention reside in the circuits andarrangements hereinafter more fully described with reference to theaccompanying drawing, in which:

Figure 1 is a schematic diagram of the connections in the modulatingsystem of our invention feeding directly to a line wire circuit; Fig. 2is a schematic diagram of the modulating system of our invention havingits output circuit connected directly in the grid input circuit of anelectron tube amplifier; and Fig. 3 is a graph of a magnetization curveshowing the method of modulating the magnetic eld.

In the system of our invention we employ an induction type mechanicaloscillator such as is shown in our copending application for Mechanicaloscillator, Serial No. 32,952, led July 24, 1935, for generating thecarrier voltage. In the case of telephonie transmission a carrier ofrelatively high frequency is desirable and this is obtained in themechanical oscillator described in our application Serial No, 32,952 byincreasing the number oi perforations in the revolving disc and/orincreasing the speed of rotation of the disc.

The modulating system of our invention comprises a mechanical oscillatoradapted for gen- 5 erating directly a modulated wave by the employmentof a modulated magnetic eld, the high frequency voltage being generatedin proportion to the amount of ux in the eld at any instant.

In order to accomplish this effect, a magnetic 10 circuit of specialarrangement and operating under prescribed conditions is provided, aswill be hereinafter more fully disclosed.

Referring to the drawing in more detail, Fig. l shows diagrammaticallythe elements and the l5 connections in one form of the System of ourinvention. The mechanical oscillator comprises a core structure 22 and arotatably driven disc l which is composed of magnetic material and hasperforations 2 therein adapted to pass between 20 pairs of pole pieces 3and 3a, 3' and 3a', blocking the passage of the flux through one of thesets of pole pieces, for example, 3 and 3', while a portion of the disclies between the pole pieces of the other set 3a, 3a', permitting thepassage of the iiux therethrough. As the disc rotates the flux passesalternately through the sets of pole pieces. Inductor coils 5 and 5 aremounted on the portions 6 and 6 of the core 22 disposed on oppositesides of the disc I, between pole pieces of dif- 30 ferent sets. In thisposition, the coils 5 and 5' are linked by the flux in each shiftthereof from the one set of pole pieces to the otherF The flux isproduced by the coils 4 and 4 which are mounted on the portions 'l and Tat oppo- 3- site ends of the core structure. Coils 4 and 4 are shownconnected in series with the output of the audio frequency amplifier 8.The coils 4 and ll are wound and connected in such a manner that thepoles adjacent the portion 5 of the core vary always in the samepolarity, as also do the poles adjacent portion 6. The combined flux ofboth coils 4 and 4 is, therefore, passed through one or the other set ofpole pieces; and since in shift* ing from one set of pole pieces to theother, the 4,. flux from one of the coils 4, 4', moves out of theinductor coils 5, 5', and the flux from the other coil moves in from theopposite direction substan tially all of the flux threads through theinductor coils 5, 5', to generate voitage therein, 50

t is seen also that due to the complementary arrangement oi perforations2 and solid portions of the disc l with respect to the sets of polepieces, the effective reluctance of the whole magnetic path issubstantially constant and there are no 55 flux variations in theportions l, l', of the core due to the valving of the flux by the discl. Hysteresis loss in the core is, therefore, maintained at a minimumand distortion of the modulated output due to saturation of the core isprevented.

The input of audio amplifier 3 is connected through audio transformer 9and terminals l to the source of signal energy which may be a microphonepick-up circuit, or any continuous or interrupted audio wave system.Inductor coils 5 and 5 in which the modulated high frequency voltage isgenerated are connected in series and to the utilization circuitsthrough the output terminals II. The coils 5, 5 in Fig. 1 are of lowimpedance and devised to connect directly to a transmission line.

As shown in Fig. 2, the coils 5, 5', may be made of high impedance andconnected to the input circuit IZ of an amplifier it. In this form ofour invention, the mechanical oscillator may be smaller in physical sizeand electrical capacity since it is required to generate only energysufficient to energize the grid of the amplifier I4. The output circuitof the amplifier i4 includes transformer I5, the primary of which istuned by means of condenser EB connected in parallel therewith in orderto reduce harmonics and eliminate further distortion.

Fig. 3 is a diagrammatic representation by graph of the relation betweenmagnetizing current I and resulting magnetic flux, t, and shows theoperation of the system of our invention with respect to that relation.In operation, as indicated in Fig. 3, the normal current output il ofthe amplifier 8 is such as to provide approximately one-half the flux,as denoted at i8, which may be produced in the core 22 by coils 4, 4before the core is saturated. Under this condition, an oscillation ofapproximately one-half maximum amplitude will be generated. Now, if theplate current of amplifier 8 is increased, as at I9, by reason of apositive charge on the grid of the amplifier 8 due to a signal in theinput circuit, the magnetization in the core will be increased asindicated at ISU. and a proportionately increased voltage generated inthe coils 5, 5. And conversely, a proportionately smaller flux 20a isproduced and a corresponding voltage generated in the coils 5, 5' whenthe grid of amplifier 8 is made negative and the plate current less, asat by a signal in the input circuit, Thus, signal energy of audio orvoice frequencies applied to the grid of the amplifier 8 will producecorresponding Variations in the amplitude of the magnetic field of themechanical oscillator.

The eii'ect of the rotating disc l on the pulsating magnetic eld is suchas to interrupt and reverse it in direction at high frequency, as shownin Fig. 3 at 2l and 2l. rIhe result is a modulated high frequency wave,modulated in accordance with the signal energy supplied throughterminals il), and having a frequency determined by the operation of thedisc l.

While we have described our invention in certain preferred embodiments,We desire it understood that modifications may be made and that nolimitations upon our invention are intended other than may be imposed bythe appended claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is as follows:

1. In a modulating system, a mechanical modulator-oscillator devicecomprising means for producing a magnetic field varying in intensity inaccordance with the modulating signal energy, inductor coils disposed insaid magnetic field, and means for reversing said magnetic field withrespect to said inductor coils at high frequency whereby voltage isgenerated in said inductor coils in accordance both With the intensityof the magnetic field as varied by the modulating signal energy and withthe frequency of the reversal of the magnetic field with respect to saidcoils.

2. A modulating system comprising a source of modulating energy, meansfor amplifying modulating energy from said source, means for producing amagnetic field varying in intensity in accordance with said modulatingenergy, inductor coils disposed in said magnetic fields andelectromechanical means for reversing the direction of said varyingmagnetic field in said coils at high frequency for generating a voltagein said coils in accordance with the frequency of reversal and theintensity of .said magnetic field. f

means for varying said flux substantially between its maximum density atsaturation and zero in accordance with modulating energy from saidsource, inductor coils mounted on said core and linked by said magneticflux, and electro-mechanical means for reversing the direction of saidvarying magnetic iiux in said coils at high frequency for generating avoltage in said coils in accordance with the frequency of the reversaland the density of said magnetic flux.

4. In a modulating system, a mechanical modulator device comprising asubstantially reetane gular core structure, field windings mounted onthe short arms at either end of said rectangular core structure,inductor coils mounted centrally on the long arms at either side of saidrectangular core structure, pole pieces on said core struc ture disposedat either side of each of said inductor coils and projecting inwardly ofsaid rectangular core structure in directly opposite positions, and arotatable disc member of magnetic material and having perforationsdisposed adjacent the periphery thereof mounted between said pole pieceswhereby the magnetic path through one set of said pole pieces is blockedby one of the perforations in said disc at the same instant the magneticpath between the other set of said pole pieces is made low in reluctanceby virtue of a portion of said disc of magnetic material, said disc inrotating effecting the shifting of the magnetic path alternately betweenthe sets of oppositely positioned pole pieces, and means for energizingsaid field windings from a source of modulating energy whereby a voltageis induced in said inductor coils proportional to the intensity of themagnetic field produced by said modulating energy at the frequency ofthe shifting of said magnetic eld.

5. The method of generating a modulated carrier wave which comprisesproducing a magnetic eld varying in intensity with the modulatingenergy, reversing the direction of said magnetic field at the carrierfrequency rate, and inducing by virtue of said varying and reversingfield a voltage proportional to the intensity of the varying field atthe frequency of the reversing of the field.

6. The method of generating a modulated carrier wave which comprisesproviding a magnetic field, reversing the direction of the magneticfield at the carrier frequency rate, inducing by virtue of saidreversing magnetic field a voltage at the frequency of the reversing ofthe magnetic eld, and modulating the intensity of said magnetic eldwhereby said voltage is correspondingly modulated.

7. A modulating system comprising a source of modulating energy, meansfor amplifying modulating energy from said source, amodulator-oscillator device including means for producing a magneticfield varying in intensity in accordance with said modulating energy,inductor' coils disposed in said magnetic eld, and means for reversingthe direction 0f said magnetic field with respect to said inductor coilsat high frequency whereby a modulated high frequency voltage is inducedin said inductor coils; and an output circuit connected with saidinductor coils.

8. A modulating system comprising a source of modulating energy, meansfor amplifying modulating energy from said source, amodulator-oscillator device including means for producing a magneticfield varying in intensity in accordance with said modulating energy,inductor coils disposed in said magnetic eld, and means for reversingthe direction of said magnetic field with respect to said inductor coilsat high frequency whereby a modulated high frequency voltage is inducedin said inductor coils; and an electron tube amplier having input andoutput circuits, said inductor coils being of high impedance andconnected in said input circuit.

9. A modulating system as set forth in claim 8 and having filter meansin the output circuit of said electron tube amplifier for reducing theharmonic content of the modulated output.

10. In a modulating system, a mechanical modulator-oscillator devicecomprising a core structure, eld windings mounted on said corestructure, inductor windings mounted on said core structure, means forenergizing said eld windings by modulating signal energy for producing amagnetic field adapted to link said inductor windings, and means forreversing said magnetic field with respect to said inductor windings atthe carrier frequency, whereby a modulated carrier wave is generated insaid modulator-oscillator.

JAMES D. DURKEE. EDWARD H. YONKERS.

